The present invention generally relates to overheating protection devices for rotational control apparatus and especially for rotational control apparatus for controlling air flow, specifically to overheating protection devices for fan clutches; and particularly to overheating protection devices for fan clutches for internal combustion engines.
U.S. Pat. No. 5,398,794 discloses an overheating protection device in the form of a thermal fuse for a fan clutch. Retrofitting existing fan clutches with the thermal fuse of U.S. Pat. No. 5,398,794 would be possible but generally may not be very practical because of the large number of types and configurations of existing fan clutches.
U.S. Pat. No. 5,765,672 shows an overheating protection device for interrupting actuation of a fan clutch in the event that the fan is unable to rotate for any reason. In the preferred form disclosed therein, the device has particular application when rotation is prevented by interference of the radiator and/or shroud with the fan, bearing failure in the fan clutch, and other like conditions and senses rotation of the fan by sensing the movement of air as the result of the fan rotation.
However, another reason of interface slippage in the fan clutch is low actuation air pressure. Specifically, the air pressure may be insufficient to move the interface against the bias of the springs, with the springs biasing the interfacing surfaces either together or apart. In either case, low actuation air pressure results in slippage between the interfacing surfaces.
Thus, a need continues to exist for overheating protection devices which may be easily retrofitted for use with existing fan clutches to remove the risk of reduced operational life for the friction interface disc, the friction facing, and other clutch components and to remove the risk of overheating of surrounding cooling components such as the fan belts as the result of interface slippage in the fan clutch. In this regard, a need exists for overheating protection devices which prevent actuation of or multiple attempts to actuate the fan clutch under low fluid actuation pressure.